A fuel container and delivery assembly for use with a direct oxidation fuel cell system is provided. The container and delivery assembly allows clean fuel which, in a preferred embodiment, is in the form of either pure methanol or an aqueous methanol/water mixture to be delivered to the cell. Additives are mixed with the fuel containing substance prior to release of the fuel outside of the cell. The fuel substance is housed in an inner tank, which is disposed within an outer container. A plenum area defined by the space between the outer container and the flexible bladder is filled with the additives so that, upon rupture of the entire assembly, the fuel substance is mixed with the additives. In one embodiment of the invention, the inner tank is a flexible bladder. A rupture means is provided on a needle, which draws the fuel out in pure form, tears the flexible bladder so that any remaining fuel is mixed with the additives when it is desired to dispose of or re-fill the container.